godinu,
AdSense will only allow you to show a certain number of ads on a single page at one time.. For example, if you place AdSense only in link_summary.tpl it should only display ads on the top 3 stories on your homepage or queued section. When someone opens a directly story link, it would obviously only show one.
I've been playing around with which ad formats work best. I will say that I am not very happy with the keyword matching google uses to determine ads... For example my pligg site is about funny videos, and google places some REALLY strange ads on the site that have no relevance to the content... Take the the latest video, its titled "Obsessive compulsive cat flushing the toilet" The Google ads are about "stress relief"
You can see my AdSense wrapped pligg site at
http://scooptube.com
Hope that helps, and if you have any questions feel free to ask...